To collect oil effectively from the surface of water is difficult. It is particularly difficult to collect oil during winter from among ice blocks. Whether it be docks, natural shores or open water, it is not possible to collect oily ice blocks; instead, the oil must be separated from ice in the water before recovery. The prior art is disclosed in patent publications FI106969, FI80746, FI75014 and FI73029. These all encompass the same principle, i.e. the vessel includes a sloping screen surface driven towards an oily mass of ice blocks so as to force the ice deeper while the oily water freed from the ice is provided onto the screen surface. The oil can then be recovered in the normal way.
The problem in the solutions of the prior art is the rigidity and inadaptability as to the use of the devices. The vessel is just steered straight forward and only a strip as wide as the screen surface can be cleared in the area that needs to be cleared. In narrow shipping routes, in docks and by the shores, the vessels are more likely to just stir the oily mass of ice, and effective clearing is far from being achieved. In addition, the reversing and returning over and over makes the operation very slow and ineffective.